Ostracoda

Chapter · April 2006with7 Reads
DOI: 10.1007/0-306-47671-1_7
Abstract
Ostracods are small bivalved crustaceans that are common in non-marine waters. They secrete shells of low-Mg calcite, which are often well preserved in Quaternary sediments. Ostracods are sensitive to a range of ecological factors, of which habitat type and the chemical composition are potentially most valuable for palaeoenvironmental work. Furthermore, ostracod shells provide a source of carbonate for geochemical analysis, including trace elements and stable isotopes. Despite past under-representation of ostracods in palaeolimnology, recent advances in the understanding of their biology, taxonomy, ecology and shell chemistry have led to them becoming used almost routinely in environmental reconstruction alongside other indicators. This chapter reviews the palaeolimnological significance of ostracods by providing an outline of their biology, taxonomy and ecology, together with an account of the main palaeoenvironmental techniques and their application.
  • [Show abstract] [Hide abstract] ABSTRACT: Pollen, chironomid, and ostracode records from a lake located at alpine treeline provide regional paleoclimate reconstructions from the southwest Yukon Territory, Canada. The pollen spectra indicate herbaceous tundra existed on the landscape from 13.6–11 ka followed by birch shrub tundra until 10 ka. Although Picea pollen dominated the assemblages after 10 ka, low pollen accumulation rates and Picea percentages indicate minimal treeline movement through the Holocene. Chironomid accumulation rates provide evidence of millennial-scale climate variability, and the chironomid community responded to rapid climate changes. Ostracodes were found in the late glacial and early Holocene, but disappeared due to chemical changes of the lake associated with changes in vegetation on the landscape. Inferred mean July air temperature, total annual precipitation, and water depth indicate a long-term cooling with increasing moisture from the late glacial through the Holocene. During the Younger Dryas (12.9–11.2 ka), cold and dry conditions prevailed. The early and mid-Holocene were warm and dry, with cool, wet conditions after 4 ka, and warm, dry conditions since the end of the Little Ice Age.
    Article · Feb 2009
  • [Show abstract] [Hide abstract] ABSTRACT: Luoto, T. P. 2009: An assessment of lentic c eratopogonids, ephemeropterans, trichopterans and oribatid mites as indicators of past environmental change in Finland. — Ann. Zool. Fennici 46: 259–270. I studied a dataset of surface sediment samples from 80 lakes with zoological macrore-main analysis to assess the potential of fossil ceratopogonids (Diptera: Ceratopogoni-dae), ephemeropterans (Insecta: Ephemeroptera), trichopterans (Insecta: Trichoptera) and oribatid mites (Acarina: Oribatida) as palaeolimnological indicators in Finland. Results showed that late-winter hypolimnetic oxygen and climatic variables were most important in infl uencing the occurrence and abundance of these taxa. Of the ceratopo-gonids, the Bezzia type was an indicator of elevated hypolimnetic oxygen conditions, warm climate and oligotrophy, while the Dasyhelea type indicated low hypolimnetic oxygen conditions, moderately cool climate and mild acidity. Ephemeropterans, tri-chopterans and oribatids indicated warm climatic conditions and oribatids were also indicative of elevated oxygen conditions and small oligotrophic lakes. Results of this study can be useful in palaeolimnological studies because the fauna examined provides a valuable supplementary data source for multiproxy studies.
    Full-text · Article · Aug 2009
  • [Show abstract] [Hide abstract] ABSTRACT: Seven species of freshwater ostracodes were identified from the sediments of 43 lakes on eight islands across the Canadian Arctic Archipelago. No ostracodes were encountered in the sediments of almost half of the lakes, and most were found at sites that had higher alkalinity. Several taxa endemic to Arctic regions are found across the Arctic Archipelago, including Candona rectangulata Alm, Limnocythere liporeticulata Delorme, and Tonnacypris glacialis sars. The distributions of Cytherissa lacustris sars, Cyclocypris globosa sars, Limnocythere sappaensis staplin, and Limnocythere (Limnocytherina) camera Delorme are more limited; this fact is attributed to differences in ion composition and concentrations. RÉSUMÉ. Sept espèces d'ostracodes d'eau douce ont été identifiées à partir des sédiments de 43 lacs répartis dans huit îles de l'archipel Arctique canadien. Aucun ostracode n'a été décelé dans les sédiments de près de la moitié des lacs, et la plupart ont été trouvés dans des lieux ayant un taux d'alcalinité plus élevé. Plusieurs taxons endémiques aux régions de l'Arctique se retrouvent à la grandeur de l'archipel Arctique, dont le Candona rectangulata Alm, le Limnocythere liporeticulata Delorme et le Tonnacypris glacialis sars. Les répartitions de Cytherissa lacustris sars, de Cyclocypris globosa sars, de Limnocythere sappaensis staplin et de Limnocythere (Limnocytherina) camera Delorme sont plus restreintes, ce qui est attribuable aux différences sur le plan de la composition et des concentrations en ions. Mots clés : ostracodes, répartitions, biogéographie, limnologie, paléolimnologie, Arctique canadien Traduit pour la revue Arctic par nicole Giguère.
    Full-text · Article · Sep 2009
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